1. Field of the Invention
This invention relates to a rotor for an impact crusher with a vertically extending rotor shaft and at least one stellate plate connected thereon and locked against rotation, on which a plurality of replaceable attached hammer tools are mountably attached in a relative distance to a center of the rotor disc by different replaceable adapter pieces.
2. Discussion of Related Art
Impact crushers are used in a variety of different technical fields, whereby only the use regarding the separation and delamination, respectively, of compound materials is of interest. Such compound materials can be compounds of metal/metal, plastic/plastic, metal/plastic or mineral compounds with metals and/or plastics. Because the physical properties of the individual components of the compounds are different, such compound particles are separated in impact crushers and with each impulse different materials deform unequally elastically and unequally plastically and thereby separate. Typical compound materials which are processed by the applicant are, for example, electronic waste and shredder waste, such as residue from the shredder (RESH), shredder light fractions (SLF) or automotive shredder residues (ASR) from car recycling.
The use of impact crushers in this area is associated with enormous wear of the hammer tools. This is quite contrary to hammer mills which are used for grinding of grain products, particularly in the food processing industry. An example of such a hammer mill is described in German Patent Reference DE-10 355 119 A.
Many impact crushers work with hammer blades, which are mounted across the entire effective range of the rotor shaft and extending parallel thereto. There are two versions known, namely embodiments in which the hammer blade is designed as a reversible hammer blade and thus can be reversed by 180° after a wearout of the one side and is usable again so that another tool life is available. Because such reversible hammer blades are not adjustable in radial direction they are implementable only in areas in which the abrasion per time unit is relatively small. With the abrasion, the blade not only becomes thinner but also the radial distance of the hammer blades decreases. This is not attributed to the areas of the hammer blade being located further to the outside which are moved with higher speed and thus also the respective impulses are higher and hence the abrasion is higher. If the hammer blade wears out at the outer edge, the gap between the hammer blade and the crusher walls increases and the efficiency of the mill is automatically reduced. An example of an impact crusher rotor with a reversible hammer blade is described, for example, in European Patent Reference EP-0 945 181 A. For the use in the field of compound material delamination, particularly for shredder waste from scrapped car disposal and electronic waste, constructions of the known type are hardly suitable. Besides the extremely high wear in these areas, additionally an extreme deposit of particles with partly oily portions occurs, whereby particles are deposited everywhere on the rotor. When the hammer blades have to be replaced or reversed, the respective screw connections, which serve for clamping the blades, have to be loosened. This is basically impossible without intensive cleaning.
In a very unconventional construction, in which the rotor shaft is of a casing formed of rings connected through circumferential weld seams, hammer tools, which are retained by axially parallel rods penetrating the discs can be inserted between the individual ring segments. Also, along with the wear of the tools the space between the ends of the hammer tools and the crusher wall of the stator also increases constantly and hence the efficiency of the mill is decreased.
An impact crusher with a rotor is known from PCT Patent Reference WO 00/53324-A. The rotor of this impact crusher includes a stellate plate having horseshoe-shaped hammer tools, the free ends of which are at least approximately facing radially outwards. Within the inner free space of these horseshoe-shaped hammer tools adapter pieces are mounted, which can be replaced depending on the wear of the hammer tools, so as to bring the free ends closer again to the crusher walls of the stator. Thus, the distance between these free wearing ends of the horseshoe-shaped hammer tools can be adjusted within a relatively tight range regarding the distance of these free ends and the crusher wall at the stator and thus the efficiency of the system can be maintained. The adaptors are not subject to abrasion and are replaced depending on the requirements. The impact crushers of interest herein have a rotor diameter of, for example, 1 to 2 meters and rotate with a speed of between 1000 to 3000 rpm. This results in circumferential speeds of up to 500 km/h. In case of larger elements getting into such an impact crusher or if certain lumps are building up by coincident, the torque during a drum blockade would be so high, that the rotor as well as the stator would be damaged. Because the adaptors are mounted on the stellate plate by a bolt or a screw, the adaptors can rotate but the occurring torque impulse is enormously high. The arrangement with a one-sided support of the adaptor above the stellate plate results in a disadvantageous force transmission and accordingly subsequent damages through a shearing bolt or screw, with which an adaptor is mounted on the stellate plate, can occur.
Another problem of this known rotor for an impact crusher is that the material portion of the hammer tools, which is not available for abrasion, is very high. Optimally calculated only 20 to 30% of the volume of the hammer tools are available for abrasion. This however increases the overall production cost.